1. Field of the Invention
The present invention relates in general to transistorized electrosurgical units and more specifically to such units that selectively provide high frequency, high voltage level, cutting or coagulation currents.
2. Description of the Prior Art
A wide variety of electrosurgical units for generating cutting and coagulation currents are known in the art. The earliest of these units include spark gaps and/or electronic circuits with vacuum tubes and they have provided reasonably good high frequency surgical currents at high power levels. However, a major drawback with spark gap and the tube units is that they are inherently unreliable and bulky. Recently, various electrosurgical unit manufacturers have attempted to provide transistorized units.
Various types of transistorized units are shown in U.S. Pat. Nos. 3,885,569, 3,699,967 and 3,675,655. The primary advantage that transistorized units have provided over tube or spark gap type units in that they are significantly smaller in size and lighter in weight than spark gap or tube units and they are more reliable. However, a problem with heretofore known transistorized units is that none are able to provide both high voltage level operation as well as high frequency currents. This is because power transistors with unusally high voltage ratings must be employed to provide the most desirable voltage levels for for optimum operation. Accordingly, in prior art circuits, rapid switching of such high voltage power transistors has not been achieved. While lower power transistors can be and are employed in units presently on the market in order that high frequency currents can be achieved, such units suffer from a lack of sufficient voltage for most effective operating conditions.
The present invention provides a transistorized electrosurgical unit that not only generates high frequency cutting and coagulation currents but also provides high voltage level outputs.